The posts above dated in June 2019 could really be for older years and may not apply to 2020. When they started this new forum all the prior posts got dated for 2019.
You have to be using the Desktop program to do 2020 now. Do you have withholding on your 1099B? After you fill in the first screen with sale date and proceeds etc. you will get this next screen that has a box 4 for withholding.